The initial thrust of the proposed research is to use fluorescent double-stranded DNA to ingredients for synthesizing the requisite DNA derivatives are reaction of single-stranded DNA with chloroacetaldehyde and a thermal reannealing step. The known properties of recA protein dictate the nature of the DNA materials to be employed in these syntheses. Those materials should enable us to develop a novel method for monitoring strand transfer reactions continuously with both stopped-flow and steady-state fluorometers. The second major focus of the proposal is the utilization of fluorescent single-stranded DNA to test proposed mechanisms for recAp-catalyzed reactions. In all, the experiments suggested here should afford new insights into the mechanism of genetic recombination, one of the most fundamental biological processes.